This invention relates to electronic amplifiers. In particular, this invention relates to amplifiers, including radio frequency signal amplifiers, that are linearized by using negative feedback.
When an amplifier circuit is used to amplify signals having a high peak power level to average power level power ratio (high peak-to-average power ratio) it is desirable to operate the amplifier at the highest average power level possible. (Voice signals have a high peak to average signal power ratio as well as certain types of quadrature modulation signals, typically used with digital signals.) When an amplifier saturates on modulation peaks, the linearizing effect of negative feedback is lost and it can generate harmonics or other spurious signals. If a saturated amplifier is used in communications applications where there may be several frequency-adjacent communications channels, the harmonics and other spurious outputs caused by the overdriven amplifier can spill over or splatter into channels occupying adjacent frequencies adversely affecting signals in adjacent frequency channels. Controlling or limiting the saturation of an amplifier used in such applications can avoid this adjacent channel signal splatter.
It is desirable to operate an amplifier at as high an output power level as possible without overdriving the amplifier. A negative feedback amplifier that is capable of dynamically adjusting input signal levels to the amplifier in response to the rate of occurence of saturation would be able to maintain maximum output power levels while minimizing spurious signals caused by saturation.